matrix multiplication



I am having trouble with matrix multiplication and I don't understand
what the problem is.  I want to multiply a 3x3 matrix bya column
vector, and I can't seem to make it work.

Specifically, I have a function defined:
Ry(thy):=matrix([cos(thy),0,-sin(thy)],[0,1,0],[sin(thy),0,cos(thy)])$

I call
R2:Ry(th);

and then I try and create a column vector:
cv:matrix([0],[0],[1]);

and try
R2.cv;

and I get the message that the dimensions are incompatible.

What am I doing wrong?  R2 appears to be 3x3 on the screen and cv
displays as a 3x1.

Thanks,

Ryan